Anti-lock braking systems (ABS) function as part of overall vehicle braking systems to prevent the vehicle's wheels from locking or excessively slipping while a driver brakes the vehicle, improving both brake feel and driver control of the vehicle. Anti-lock braking can be automatically initiated by an ABS controller once the wheel speed in at least one wheel of the vehicle drops a predetermined amount in comparison to vehicle speed over a predetermined time period, that is, when a wheel slip threshold is reached. However, a single wheel slip threshold is not sufficient to account for different environmental conditions that can occur during some instances of vehicle braking, such as environmental conditions including rain, snow, sleet, potholes, and speed bumps.